System and process to control electroplating a metal onto a substrate

ABSTRACT

An electroplating system is provided with a rotatable head assembly including a substrate holder to secure a substrate for entry into a bath of electrolyte; and a head tilt mechanism including a stepper motor connected to the rotatable head assembly and configured to control bath entry parameters for optimal surface wetting of the substrate, upon bath entry for electroplating the substrate free of electroplating defects, including, but not limited to, swirl defects.

FIELD

[0001] The present invention relates generally to the manufacture of semiconductor devices and, more specifically, relates to an electroplating system and process to control electroplating, also known as electrochemical deposition (ECD), a metal onto a semiconductor substrate.

BACKGROUND

[0002] Conventional semiconductor devices comprise a semiconductor substrate, typically doped silicon, and a plurality of sequentially formed dielectric inter-layers and conductive patterns. An integrated circuit is formed containing a plurality of conductive patterns comprising conductive lines separated by inter-wiring spacings, and a plurality of interconnect lines, such as bus lines, bit lines, word lines and logic interconnect lines. Typically, the conductive patterns on different layers, i.e., upper and lower layers, are electrically connected by a conductive plug filling a via hole, while a conductive plug filling a contact hole establishes electrical contact with an active region on a semiconductor substrate, such as a source/drain region. Conductive lines are formed in trenches which typically extend substantially horizontal with respect to the semiconductor substrate. Semiconductor “chips” comprising five or more levels of metallization are becoming more prevalent as device geometric shrink to sub-micron levels.

[0003] Aluminum (Al) has traditionally been the choice of conductive materials used in interconnect metallization. However, smaller feature sizes have created a need for a conductive material with lower resistivity and higher current carrying capacity than aluminum. Copper (Cu) and its alloys have recently been considered as a candidate for replacing or at least complementing aluminum (Al). However, choices of methods for depositing copper into features having a high aspect ratio in sub-quarter micro features are limited because common chemical vapor deposition (CVD) and physical vapor deposition (PVD) processes can be costly and have provided unsatisfactory results for commercial production requirements, such as high throughput, low defects, and consistent uniformity. As a result, electroplating or electrochemical deposition (ECD) is becoming an accepted method for forming interconnection features in semiconductor devices.

[0004] In general, metal electroplating or electrochemical deposition (ECD) is a wet process using electrolyte (i.e., plating solution that contains chemicals such as copper sulfate that is a source of copper for the electroplating process) and can be achieved by a variety of techniques. However, there are often occurrences of one or more electroplating defects and other non-uniformities in interconnect features. For example, one type of electroplating defects commonly occurring as a result of electroplating processes is a swirl defect, which is a defect that generally appears with a swirl-like pattern. A swirl defect, along with other defects, can cause appreciable number of devices on a substrate to be rendered useless. Another problem in metal electroplating is that the various processes required are time consuming and may involve the use of a number of different pieces of equipments and/or tools. As a result, the throughput, or the number of substrates (wafers) capable of being processed during a given time frame, is reduced.

[0005] Accordingly, there is a need for an improved electroplating system and process that eliminate electroplating defects, including, but not limited to, swirl defects and increase throughput and enable high volume processing.

BRIEF DESCRIPTION OF THE DRAWING(S)

[0006] A better understanding of the present invention will become apparent from the following detailed description of example embodiments and the claims when read in connection with the accompanying drawings, all forming a part of the disclosure of this invention. While the following written and illustrated disclosure focuses on disclosing example embodiments of the invention, it should be clearly understood that the same is by way of illustration and example only and that the invention is not limited thereto. The spirit and scope of the present invention are limited only by the terms of the appended claims. The following represents brief descriptions of the drawings, wherein:

[0007]FIG. 1 illustrates an example plating system for electroplating a metal onto a substrate;

[0008]FIGS. 2A-2B illustrate an example wafer (substrate) with electroplating defects such as swirl defects;

[0009]FIG. 3 illustrates another example plating system for electroplating a metal onto a substrate;

[0010]FIG. 4 illustrates an example plating system including a motorized head tilt mechanism and related software necessary for controlling an electroplating process to eliminate electroplating defects, including, but not limited to, swirl defects according to an embodiment of the present invention;

[0011]FIG. 5 illustrates an example control operation between a tool embedded controller (CPU) and a stepper motor according to an embodiment of the present invention;

[0012]FIG. 6 illustrates an example command execution between a tool embedded controller (CPU) and a stepper motor according to an embodiment of the present invention; and

[0013]FIG. 7 illustrates an example command operation between a tool embedded controller (CPU) and a stepper motor according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0014] Before beginning a detailed description of the subject invention, mention of the following is in order. When appropriate, like reference numerals and characters may be used to designate identical, corresponding or similar components in differing figure drawings. Further, in the detailed description to follow, example sizes/values/ranges may be given, although the present invention is not limited to the same.

[0015] The present invention is applicable for use with all types of semiconductor wafers and integrated circuit (IC) devices, including, for example, MOS transistors, CMOS devices, and MOSFETs, which may become available as semiconductor technology develops in the future. However, for the sake of simplicity, discussions will concentrate mainly on exemplary use of electroplating (or depositing) a metal onto a silicon substrate, although the scope of the present invention is not limited thereto. The term “metal” as will be described herein below, refers to copper “Cu”, but is not limited thereto. The terms “substrate,” “silicon substrate” and “wafer” may be used interchangeably herein below. A standard substrate may be a 12 inches wafer but is not limited thereto.

[0016] Attention now is directed to the drawings and particularly to FIG. 1, in which an example electroplating system 100 is illustrated. FIG. 1 illustrates an example plating system 100 for electroplating a metal onto a substrate 10. As shown in FIG. 1, the substrate 10 may be secured onto a substrate holder 110 positioned above a cylindrical electrolyte container 120 with the plating surface facing an opening of the cylindrical electrolyte container 120. The electrolyte may be pumped into the cell through an electrolyte inlet 130 to flow upwardly to contact the substrate plating surface. An electrical power supply 140 may be connected to a cathode contact member 142 and an anode 144 of the plating system 100. The cathode contact member 142 of the plating system 100 delivers an electrical current (i.e., a forward plating current) through a seed layer formed on the substrate 10 to induce the metal ions in the electrolyte to deposit onto the exposed conductive surface of the substrate 10. The anode 144 may be disposed in the electrolyte and electrically biased to attract the negatively charged counterparts of the metal ions in the electrolyte so that the metal ions can be deposited on the exposed conductive surface of the substrate 10. The substrate 10 may then be removed from the electrolyte and metal deposits can dry on the surface of the substrate 10.

[0017] However, the metal deposit on the substrate 10 using the electroplating system shown in FIG. 1, typically contain electroplating defects 12, such as, swirl defects and other non-uniformities in interconnect features. An example swirl defect in the substrate (wafer) 10 can be shown in FIG. 2A. Such electroplating defects 12 may include one or more lines of one or more pits/voids 14 in the plated metal film (pit defects of missing copper “Cu”) as shown by scanning electron microscope in FIG. 2B, which can cause appreciable number of devices on a substrate 10 to be rendered useless. Other random scattered defects shown in FIG. 2A may represent small bumps of copper “Cu” which extend above the surface of the plated substrate 10. However, these scattered defects do not cause yield loss on the plated substrate 10. Another problem in metal electroplating using the system shown in FIG. 1 is that the various manufacture processes required are time consuming and may involve the use of a number of different pieces of equipments and/or tools. As a result, the throughput, or the number of substrates (wafers) capable of being processed during a given time frame, is reduced.

[0018]FIG. 3 illustrates another example electroplating system for electroplating a metal onto a substrate with improved throughput. As shown in FIG. 3, the electroplating system 300 generally comprises a rotatable head assembly 320, an electrolyte collector 340, and a head assembly frame 360. The rotatable head assembly 320 includes a mounting plate 322, a head tilt actuator 324, a shaft 326, a substrate holder assembly 328 including a substrate holder 330 to secure a substrate (wafer) 10 via an annular contact ring (not shown) having a plurality of conducting members disposed thereon to support, during processing, a substrate 10 and provide a current thereto. The head assembly frame 360 typically includes a mounting post 362, a shaft 364, a post cover 366, a cantilever arm 368, a cantilever arm actuator 370, and a pivot joint 372.

[0019] The mounting post 362 may be mounted onto the body of a mainframe, and the post cover 366 covers a top portion of the mounting post 362. The mounting post 362 provides rotational movement of the head assembly frame 360 about a substantially vertical axis that extends through the mounting post 362 in a direction indicated by arrow A1. Such a motion is generally provided to align the rotatable head assembly 320 with the electrolyte cell 340.

[0020] One end of the cantilever arm 368 may be pivotally connected to the shaft 364 of the cantilever arm actuator 370. The cantilever arm actuator 370 is a pneumatic air cylinder used to enable the cantilever arm 368 to control entry of the rotatable head assembly 320 into the electrolyte cell 340 for an electroplating bath. The cantilever arm 368 is pivotally connected to the mounting plate 322 of the rotatable head assembly 320 at the pivot joint 372. The cantilever arm actuator 370 is mounted to the mounting post 362. The pivot joint 372 is rotatably mounted to the frame cover 366 so that the cantilever arm 368 can pivot about the frame cover 366 at the pivot joint 372. Actuation of the cantilever arm actuator 370 provides pivotal movement, in a direction indicated by arrow A2, of the cantilever arm 368 about the pivot joint 372.

[0021] The rotatable head assembly 320 may be attached to a mounting plate 322 at the head assembly frame 360. The mounting plate 322 is disposed at the distal end of the cantilever arm 368. Rotation of the rotatable head assembly 320 about the pivot joint 372 causes tilting of a substrate (wafer) 10 held within the substrate holder assembly 328 of the rotatable head assembly 320 about the pivot joint 368. When the cantilever arm actuator 370 is retracted, the cantilever arm 368 raises the head assembly 320 away from the electrolyte cell 340 as shown in FIG. 3. This tilting of the rotatable head assembly 320 effects tilting of the substrate relative to horizontal. Such tilting of the substrate can be used during removal and/or immersion of the substrate holder assembly 328 from/to the electrolyte solution within the electrolyte cell 340. When the cantilever arm actuator 370 is extended, the cantilever arm 368 rotates the head assembly 320 toward the electrolyte cell 340 to displace the substrate, in a tilted orientation, into the electrolyte cell 340.

[0022] The rotatable head assembly 320 includes a head lift actuator 324 slidably connected to the mounting plate 322. The mounting plate slide 322 guides the vertical motion of the rotatable head assembly 320. The shaft 326 of the head lift actuator 324 is inserted through a lift guide (not shown) attached to the body of the rotating actuator 324 to displace the rotatable head assembly 320, in a substantially vertical direction indicated arrow A3. A head lift actuator 324 is disposed on the mounting plate 322 to provide motive force for vertical displacement of the head assembly 320 by rotating the shaft 326. This vertical displacement of the rotatable head assembly 320 can be used to remove and/or replace the substrate holder assembly 328 from the electrolyte cell 340. Removing the substrate 10 from the electrolyte cell 340 is necessary to position the substrate 10 so that other mechanisms, not shown, can remove the substrate 10 from the rotatable head assembly 320.

[0023] The rotating actuator 324 is connected to the substrate holder assembly 328 through the shaft 326 and rotates the substrate holder assembly 328 in a direction indicated by arrow A4. The rotation of the substrate during the electroplating process generally enhances the result of metal film deposition, when the substrate 10 is immersed in the electrolyte solution. The head assembly 320 can also be rotated as the head assembly 320 is lowered to position the substrate 10 in contact with the electrolyte solution in the process cell as well as when the head assembly 320 is raised to remove the substrate 10 from the electrolyte solution in the process cell.

[0024] While the electroplating system 300, shown in FIG. 3, can improve throughput, the metal deposit on the substrate 10 still contains electroplating defects, such as, swirl defects including pits of missing metal such as copper “Cu” shown in FIGS. 2A-2B. Electroplating defects, such as, swirl defects, as previously discussed, can impact or “kill” one or more production die on the substrate 10. This is because the electroplating system 300 shown in FIG. 3 is a gravity-based descent system in which the plating bath entry is controlled by pneumatic air cylinders. Air pressure is used to move the head assembly into position for an electroplating bath. However, the electroplating system 200 using the pneumatic air cylinders, as shown in FIG. 3, is difficult to set-up and control the bath entry parameters, particularly, the substrate (wafer) rotation, the height above the plating bath prior to entry, the angle of entry into the plating bath, and the time required for bath entry. As a result, variations in bath entry parameters often exist, and such an electroplating system is inadequate to control the bath entry process for both precision and repeatability. In other words, the existing electroplating system, as shown in FIG. 1 and FIG. 3, not only fails to provide the precise control required for the electroplating process, but is also unable to make the electroplating process, i.e., bath entry process repeatable to eliminate electroplating defects such as swirl defects.

[0025] Turning now to FIG. 4, an example electroplating system including a motorized head tilt mechanism and related software necessary for controlling an electroplating process to eliminate electroplating defects, such as, swirl defects, increase throughput and enable high volume processing according to an embodiment of the present invention is illustrated. According to an embodiment of the present invention, the motorized head tilt (MHT) mechanism advantageously utilizes one or more stepper motors implemented in combination with necessary software, i.e., stepper motor controller, to precisely control the bath entry process, including the bath entry velocity and acceleration, in order to make the bath entry process repeatable and free of electroplating defects, including, but not limited to, swirl defects. The use of one or more stepper motors offers several advantages, including the ability to quickly initiate and stop rotation movement of internal moving components and control precisely each step of the bath entry process. In addition, such a motorized head tilt (MHT) mechanism can be automated to control bath entry parameters such as velocity and acceleration, in order to eliminate variations in the bath entry parameters and to reduce the time required to set-up the bath entry parameters which were previously and iterative time consuming process. As a result, optimal surface wetting of the substrate (wafer) upon bath entry can be obtained, allowing uniform plating to occur.

[0026] As shown in FIG. 4, the electroplating system 400 comprises a rotatable head assembly 420, an electrolyte collector (cell) 440, and a motorized head tilt mechanism 460. According to an embodiment of the present invention, the rotatable head assembly 420 includes a mounting plate 422, a stepper motor 424 (serving as a head tilt actuator), a shaft 426, a substrate holder assembly 428 including a substrate holder 430 to secure a substrate (wafer) 10 via an annular contact ring (not shown) having a plurality of conducting members disposed thereon to support, during processing, and provide a current thereto upon application of a specific voltage. The substrate holder assembly 428 can displace a substrate (wafer) 10 vertically, or tilt a substrate (wafer) 10 from horizontal, to suitably position the substrate (wafer) 10 between various heights and positions necessary for immersion or removal from the electrolyte solution.

[0027] The electrolyte collector (cell) 440 contains electrolyte used for the electroplating (electrochemical deposition) process. Typically, the electrolyte collector 440 may include an anode base (not shown) installed at the bottom to receive electric power, and a top cover (not shown) that is removable for anode replacement and/or repair. In addition, an electrolyte inlet and outlet may also be disposed through the bottom of the electrolyte collector 440 to circulate the electrolyte through the electrolyte collector 440, often through tubes, hoses, pipes and other fluid transfer connectors (not shown) that are known to one skilled in the art and, as a result, need not be described herein.

[0028] In general, the electrolyte within the electrolyte collector 440 is pumped to flow upwardly and contact the substrate plating surface. The electrolyte may then be recirculated and replenished to maintain the desired chemistry adjacent to the substrate seed layer (i.e., a “copper” seed layer applied to selected substrate surfaces on which the metal film is to be deposited thereon to fill or metallize the interconnect features on the substrate) in order to perform the electroplating process. For copper metalization, the electrolyte solution may comprise, for example, copper sulfate (CuSO₄) having a molar concentration between 0.5M and 1.1M; hydrogen chloride (HCl) at a concentration between 50 ppm and 100 ppm; a carrier additive such as glycol, at a concentration between 12.5 ml/l and 20 ml/l; and hydrogen sulfate (H₂SO₄) having a concentration less than 2%. However, other electrolyte composition may also be available.

[0029] The motorized head tilt mechanism 460 comprises a mounting post 462, a stepper motor 464, a post cover 466, a cantilever arm 468, a cantilever connector 470, and a pivot joint 472.

[0030] The mounting post 462 is mounted onto the body of a mainframe, and the post cover 466 covers a top portion of the mounting post 462. The mounting post 462 provides rotational movement of the motorized head tilt mechanism 460 about a substantially vertical axis that extends through the mounting post 462 in a direction indicated by arrow A1. Such a motion is generally provided to align the rotatable head assembly 420 with the electrolyte cell 440.

[0031] The cantilever arm 468 is pivotally connected to the stepper motor 464 at the connector 470, and to the mounting plate 422 of the rotatable head assembly 420 at the pivot joint 372. The stepper motor 464 is used to enable the cantilever arm 468 to control entry of the rotatable head assembly 420 into the electrolyte cell 440 for an electroplating bath.

[0032] The pivot joint 472 is rotatably mounted to the post cover 466 so that the cantilever arm 468 can pivot about the post cover 466 at the pivot joint 472. The stepper motor 464 provides pivotal movement, in a direction indicated by arrow A2, of the cantilever arm 468 about the pivot joint 472.

[0033] The rotatable head assembly 420 may be attached to a mounting plate 422 at the motorized head tilt mechanism 460. The mounting plate 422 is disposed at the distal end of the cantilever arm 468. Rotation of the rotatable head assembly 420 about the pivot joint 472 causes tilting of a substrate (wafer) held within the substrate holder assembly 428 of the rotatable head assembly 420 about the pivot joint 468. When the stepper motor 464 is retracted, the cantilever arm 468 raises the head assembly 420 away from the electrolyte cell 440 as shown in FIG. 4. This tilting of the rotatable head assembly 420 effects tilting of the substrate (wafer) 10 relative to horizontal. Such tilting of the substrate (wafer) 10 can be used during removal and/or immersion of the substrate holder assembly 428 from/to the electrolyte solution within the electrolyte cell 440. When the stepper motor 464 is extended, the cantilever arm 468 rotates the head assembly 420 toward the electrolyte cell 440 to displace the substrate, in a tilted orientation, into the electrolyte cell 440.

[0034] The rotatable head assembly 420 includes a head lift (rotating) motor 424 slidably connected to the mounting plate 422. The mounting plate slide 422 guides the vertical motion of the rotatable head assembly 420. The shaft 426 of the rotating motor 424 is inserted through a lift guide (not shown) attached to the body of the rotating motor 424 to displace the rotatable head assembly 420, in a substantially vertical direction indicated arrow A3. A rotating motor 424 is disposed on the mounting plate 422 to provide motive force for vertical displacement of the head assembly 420 by rotating the shaft 426. This vertical displacement of the rotatable head assembly 420 can be used to remove and/or replace the substrate holder assembly 428 from the electrolyte cell 440. Removing the substrate (wafer) 10 from the electrolyte cell 440 is necessary to position the substrate (wafer) 10 so that other mechanisms, not shown, can remove the substrate (wafer) 10 from the rotatable head assembly 420.

[0035] The rotating motor 424 is connected to the substrate holder assembly 428 through the shaft 426 and rotates the substrate holder assembly 428 in a direction indicated by arrow A4. The rotation of the substrate during the electroplating process generally enhances the result of metal film deposition, when the substrate (wafer) 10 is immersed in the electrolyte solution. The head assembly 420 can also be rotated as the head assembly 420 is lowered to position the substrate (wafer) 10 in contact with the electrolyte solution in the process cell as well as when the head assembly 420 is raised to remove the substrate (wafer) 10 from the electrolyte solution in the process cell.

[0036] The head tilt motor 424 of the rotatable head assembly 420 and/or the stepper motor 464 of the motorized head tilt mechanism 460 can be optimized by software, i.e., a head tilt control program 480 designed to precisely control the bath entry process, including the bath entry velocity and acceleration, in order to make the bath entry process repeatable and free of electroplating defects, including, but not limited to, swirl defects shown in FIG. 2A. As shown in FIG. 4, the head tilt control program 480 may reside in a memory 482 of a tool embedded system controller (CPU) 484 for controlling an electroplating (electrochemical deposition) process. For instance, the head tilt program 480 can interact with a stepper motor controller (driver) 490 to determine the optimal bath entry conditions, such as the wafer rotation RPM, the height above the bath prior to entry, the angle of entry into the bath, the time taken for bath entry, and to control each step of the bath entry process, via the stepper motor 464 of the motorized head tilt mechanism 460 and the head tilt motor 424 of the rotatable head assembly 420. For example, the wafer rotation RPM may be set at 30 RPM. The height above the bath prior to entry may be set at 5 mm above bath. The angle of entry into the bath may be set at a predetermined angle “x”. The time taken for bath entry, i.e., tilt speed, may be set, for example, at 1.5 second, and the immersion time may be set, for example, at 1 second.

[0037] The head tilt control program 480 can generate step count instructions, upon request from a user (technician) to the motorized head tilt motor, i.e., the stepper motor 464 of the motorized head tilt mechanism 460 in order to move the substrate holder 430 (plating cell head) from a horizontal position to an angle position. The stepper motor 464 inside the motorized head tilt mechanism 460 may move “x” number of steps in a predetermined time interval, which moves the substrate holder 430 to its angle position. The substrate holder 430 supporting a single stack of one or more wafers, also known as “cells”, may begin spinning prior to entry into the plating cell bath.

[0038] In general, the head tilt control program 480 sends instructions to a stepper motor controller 490, via Device Net (i.e., communication protocol), which then converts the command to pulses for the stepper motor 464 to control the velocity and acceleration of the movement into the bath. The stepper motor 464 may spin in response to the command and complete the requested action in a predetermined time interval, for example, 0.75 seconds. The encoder in the stepper motor 464 may then measure the actual movement achieved due to motor pulses, and an encoder position can be reported back to the tool embedded controller (CPU) 514 via the Device Net.

[0039] The head tilt control program 480 may then verify if the substrate (wafer) 10 secured by the substrate holder 340 has reached the requested position by checking an internal home flag sensor, while monitoring velocity and acceleration parameters during the actual movement to ensure the parameters are within an acceptable tolerance band. Failure to meet performance criteria may result in tool warnings or faults depending the severity of the offset. The head tilt control program 480 provides movement commands and then polls the motor driver to ensure that the commands are proceeding per expectations.

[0040] Turning now to FIG. 5, an example control operation between a tool embedded system controller (CPU) and a stepper motor according to an embodiment of the present invention is illustrated. As shown in FIG. 5, the tool embedded system controller (CPU) 484 executes the head tilt control program 480 stored in the memory 482, upon an instruction from the user at block 510. Next, the tool embedded system controller (CPU) 484 utilizes an industry communication protocol, known as “Device Net” to establish communication with the stepper motor controller 480 at block 520. The stepper motor controller 490 then translates the command (i.e., tilt command at different angle) requested from the tool embedded system controller (CPU) 484 into pulses that can be understood by the stepper motor 464 at block 530. Upon receipt of the pulses generated from the stepper motor controller 490, the stepper motor 464 moves “x” number of steps in a predetermined time interval, which moves the substrate holder 430 to its angle position.

[0041]FIG. 6 illustrates another example command execution between a tool embedded system controller (CPU) and a stepper motor according to an embodiment of the present invention. As shown in FIG. 6, the tool embedded system controller (CPU) 484 sends tilt command to the stepper motor controller 490, via Device Net (i.e., communication protocol) at block 610. The motor controller 490 then converts the tilt command into motor pulses for the stepper motor 464 to control the velocity and acceleration of the movement into the bath at block 620. The stepper motor 464 then moves in response to the pulse input and complete the requested action in a predetermined time interval at block 630. The encoder in the stepper motor 464 then measures the actual movement achieved due to motor pulses, and sends position back to the tool embedded system controller (CPU) 514 via the Device Net at block 640.

[0042]FIG. 7 illustrates an example command operation between a tool embedded system controller (CPU) and a stepper motor according to an embodiment of the present invention. As shown in FIG. 7, the tool embedded system controller (CPU) 484 can verify if the tilt command is successful at block 710. Such verification can be performed by a series of determinations. First, the tool embedded system controller (CPU) 484 determines if the cell velocity and acceleration are within a specification at block 720. A tolerance, for example, of ±5% of a set value of velocity or acceleration for the tilt may be set. Thus, if the cell velocity and acceleration are not within a specification, the tool embedded system controller (CPU) 484 will issue a tool fault or warning at block 730. However, if the cell velocity and acceleration are within a specification, the tool embedded system controller (CPU) 484 determines if the stepper motor 464 is in a correct position at block 740. A tolerance, for example, of ±5% of a set position may also be set. Thus, if the stepper motor 464 is not in a correct position, the tool embedded system controller (CPU) 484 will issue a tool fault or warning at block 750. However, if the stepper motor 464 is in a correct position, the tool embedded system controller (CPU) 484 next determines if a home flag position (i.e., correct position indicator) is met at block 760. If the home flag position is not met, the tool embedded system controller (CPU) 484 will issue a tool fault or warning at block 770. Otherwise, the tool embedded system controller (CPU) 484 will issue an indication that the cell head movement is successful at block 780.

[0043] As described from the foregoing, the present invention advantageously provides a motorized head tilt mechanism and related software necessary for controlling an electroplating process to eliminate electroplating defects, such as, swirl defects, increase throughput and enable high volume processing according to an embodiment of the present invention is illustrated. Such a motorized head tilt (MHT) mechanism utilizes a stepper motor implemented in combination with necessary software, i.e., stepper motor controller, to precisely control the bath entry process, including the bath entry velocity and acceleration, in order to make the bath entry process repeatable and free of electroplating defects, such as, swirl defects shown in FIG. 2A. Such a motorized head tilt (MHT) mechanism can also be automated to eliminate variations in the bath entry parameters and to reduce the time required to set-up the bath entry parameters which were previously and iterative time consuming process. As a result, optimal surface wetting of the substrate (wafer) upon bath entry can be obtained, allowing uniform plating to occur.

[0044] While there have been illustrated and described what are considered to be example embodiments of the present invention, it will be understood by those skilled in the art and as technology develops that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the present invention. Many modifications may be made to adapt the teachings of the present invention to a particular situation without departing from the scope thereof. For example, the electroplating system 100 shown in FIG. 4 is merely one example in which a single stack of wafer processing according to the present invention can be used. However, such an electroplating system can be adapted to provide multi-stack wafer processing. Accordingly, it is intended, therefore, that the present invention not be limited to the various example embodiments disclosed, but that the present invention includes all embodiments falling within the scope of the appended claims. 

What is claimed is:
 1. An electroplating system comprising: a rotatable head assembly including a substrate holder to secure a substrate for entry into an electroplating bath of electrolyte; and a head tilt mechanism including a stepper motor connected to the rotatable head assembly and configured to control bath entry parameters for optimal surface wetting of the substrate, upon bath entry for electroplating.
 2. The electroplating system as claimed in claim 1, wherein the head tilt mechanism is automated to control the bath entry parameters, including velocity and acceleration, so as to eliminate variations in the bath entry parameters and to reduce the time required to set-up the bath entry parameters for optimal surface wetting of the substrate during an electroplating process.
 3. The electroplating system as claimed in claim 1, wherein the bath entry parameters include a substrate rotation RPM, a height above the bath prior to entry, an angle of entry into the bath, and a time taken for bath entry.
 4. The electroplating system as claimed in claim 2, further comprising a system controller configured to control, when a head tilt control program is executed, the stepper motor which controls the bath entry parameters and each step of the bath entry process during the electroplating process so as to make the bath entry process repeatable and the substrate free of electroplating defects, including, but not limited to, swirl defects.
 5. The electroplating system as claimed in claim 3, wherein the head tilt mechanism comprises: a mounting post mounted onto a mainframe to provide rotational movement about a substantially vertical axis that extends through the mounting post so as to align the rotatable head assembly with an electrolyte cell containing electrolyte; a post cover to cover a top portion of the mounting post; a cantilever arm pivotally connected to the stepper motor and the rotatable head assembly to control entry of the rotatable head assembly into the electrolyte cell for the electroplating bath; and a pivot joint rotatably mounted to the post cover such that the cantilever arm pivots about the post cover at the pivot joint.
 6. The electroplating system as claimed in claim 4, wherein the system controller is configured to send an instruction to a stepper motor controller, via device net protocol, which converts the instruction to pulses for the stepper motor to control the velocity and acceleration of the movement of the substrate secured by the substrate holder into the electroplating bath.
 7. The electroplating system as claimed in claim 4, wherein the system controller is configured to verify if the substrate secured by the substrate holder has reached a requested position by checking an internal home flag sensor, while monitoring velocity and acceleration parameters during the actual movement to ensure the bath entry parameters are within an acceptable tolerance band.
 8. The electroplating system as claimed in claim 7, wherein the system controller is further configured to issue a tool fault alert to alert a user to adjust the bath entry parameters, when any one of the bath entry parameters is outside of the acceptable tolerance band.
 9. A method for electroplating a substrate in an electroplating system including a stepper motor and a system controller, comprising: moving a substrate, using said stepper motor, in position for entry into an electroplating bath of electrolyte; and controlling bath entry parameters for optimal surface wetting of the substrate, using said system controller, when the substrate is moved into the electroplating bath for electroplating.
 10. The method as claimed in claim 9, wherein the bath entry parameters includes velocity and acceleration information, a substrate rotation RPM, a height above the bath prior to entry, an angle of entry into the bath, and a time taken for bath entry.
 11. The method as claimed in claim 10, wherein the system controller is configured to control, when a head tilt control program is executed, the stepper motor which controls the bath entry parameters and each step of the bath entry process during an electroplating process so as to make the bath entry process repeatable and the substrate free of electroplating defects, including, but not limited to, swirl defects.
 12. The method as claimed in claim 9, wherein the system controller is configured to send an instruction to a stepper motor controller, via device net protocol, which converts the instruction to pulses for the stepper motor to control the velocity and acceleration of the movement of the substrate into the electroplating bath.
 13. The method as claimed in claim 12, wherein the system controller is configured to verify if the substrate has reached a requested position by checking an internal home flag sensor, while monitoring velocity and acceleration parameters during the actual movement to ensure the bath entry parameters are within an acceptable tolerance band.
 14. The method as claimed in claim 13, wherein the system controller is further configured to issue a tool fault alert to alert a user to adjust the bath entry parameters, when any one of the bath entry parameters is outside of the acceptable tolerance band.
 15. Am electroplating system comprising: a rotatable head assembly including a substrate holder to secure a substrate and a stepper motor to control movement of the substrate, for entry into an electroplating bath of electrolyte for electroplating; and a head tilt mechanism including a stepper motor connected to the rotatable head assembly, configured to control bath entry parameters, including tilting the substrate at a predetermined angle for optimal surface wetting of the substrate, when the substrate is moved into the electroplating bath of electrolyte for electroplating.
 16. The electroplating system as claimed in claim 15, wherein the head tilt mechanism is automated by software to control the bath entry parameters, including velocity and acceleration, so as to eliminate variations in the bath entry parameters and to reduce the time required to set-up the bath entry parameters for optimal surface wetting of the substrate during an electroplating process.
 17. The electroplating system as claimed in claim 15, wherein the bath entry parameters include a substrate rotation RPM, a height above the bath prior to entry, an angle of entry into the bath, and a time taken for bath entry.
 18. The electroplating system as claimed in claim 15, further comprising a system controller configured to control, when a head tilt control program is executed, the stepper motor in the rotatable head assembly which control rotational movement of the substrate, and the stepper motor in the head tilt mechanism which controls the bath entry parameters and each step of the bath entry process during the electroplating process so as to make the bath entry process repeatable and the substrate free of electroplating defects, including, but not limited to, swirl defects.
 19. The electroplating system as claimed in claim 15, wherein the head tilt mechanism comprises: a mounting post mounted onto a mainframe to provide rotational movement about a substantially vertical axis that extends through the mounting post so as to align the rotatable head assembly with an electrolyte cell containing electrolyte; a post cover to cover a top portion of the mounting post; a cantilever arm pivotally connected to the stepper motor and the rotatable head assembly to control entry of the rotatable head assembly into the electrolyte cell for the electroplating bath; and a pivot joint rotatably mounted to the post cover such that the cantilever arm pivots about the post cover at the pivot joint.
 20. The electroplating system as claimed in claim 18, wherein the system controller is configured to send an instruction to a stepper motor controller, via device net protocol, which converts the instruction to pulses for the stepper motor to control the velocity and acceleration of the movement of the substrate secured by the substrate holder into the electroplating bath.
 21. The electroplating system as claimed in claim 20, wherein the system controller is configured to verify if the substrate secured by the substrate holder has reached a requested position by checking an internal home flag sensor, while monitoring velocity and acceleration parameters during the actual movement to ensure the bath entry parameters are within an acceptable tolerance band.
 22. The electroplating system as claimed in claim 21, wherein the system controller is further configured to issue a tool fault alert to alert a user to adjust the bath entry parameters, when any one of the bath entry parameters is outside of the acceptable tolerance band. 